1. Field of the Invention
The present invention relates to conduit connections used in vehicular air-conditioning systems. Specifically, the present invention relates to a conduit connection that creates a fluid-tight seal and replaces conventional methods for end-forming conduit.
2. Description of the Prior Art
Presently known in the automotive air-conditioning art are many different ways to provide a connection between different conduits, or between conduits and another component, such as a compressor, accumulator, or the like. Such conduit connections must be highly reliable and virtually leak-free. In many conventional connection methods, sealing is accomplished using O-rings seated in grooves on the outer diameter of a conduit. To provide a proper seal, dimensional accuracy and stability must be ensured by processing the conduit end-form under strictly controlled manufacturing processes. Unfortunately, conventional end-forming processes often generate aluminum particle contamination. These sharp contaminants remain in the O-ring grooves, thereby cutting the O-rings and resulting in leakage.
Likewise, conventional end-forming processes require complicated, dedicated, and therefore very expensive tooling and equipment. Manufacturing each specific end-form detail of an aluminum conduit end requires constant quality control checks for equipment, raw materials, and manufacturing variations to avoid making parts that are outside of the allowed dimensional tolerances. Therefore, conventional end-forming can be a relatively slow and costly process.
Some relatively conventional end-forming methods of the prior art are disclosed in U.S. Pat. Nos. 4,863,202 to Oldford (hereafter '202) and 5,141,262 to Bartholomew (hereafter '262). These references are directed toward fitting-in-fitting novelty, unlike the present invention, which is directed to conduit-in-fitting novelty. The '202 reference discloses a connector assembly consisting of a first fitting including a body portion and a neck portion. The neck portion includes external grooves to receive O-rings. A second fitting has a bore therethrough for receiving the first fitting. One end of the second fitting bore has an internal groove for engaging one of the O-rings that is seated in one of the external grooves of the first fitting.
Similarly, the '262 reference discloses a connector assembly consisting of a first fitting including a body portion, a shoulder portion, and a neck portion. An O-ring circumscribes the neck portion and abuts the shoulder portion. A second fitting has a bore and counterbore therethrough, for receiving the neck, shoulder, and O-ring of the first fitting. The O-ring locates square against the bottom of the counterbore. Accordingly, in both the '202 reference and the '262 reference, the O-ring recess in the first fitting is exposed and potentially contaminated by particles generated during the end-forming process. Also, the recess in the second fitting potentially enables contaminants to create leak paths in the seal.
The following references are directed to conduit-in-fitting novelty, like the present invention; however, unlike the present invention, the following references require use of several intermediate fittings. Firstly, U.S. Pat. No. 5,342,095 (hereinafter '095) to Klinger et al. discloses a high pressure quick connector in which a conduit is enclosed within an intermediate metal retainer cap, intermediate metal retaining ring, and a body. The metal retainer cap, metal retaining ring, and body all have longitudinally extending bores for receiving the conduit. Further, O-rings circumscribe the conduit diameter and pilot in a reduced diameter of the body. Additionally, there is an O-ring spacer, a compression ring, and a spring. As in the '202 and '262 references, contaminants resulting from the end-forming process may create a potential for leakage.
Secondly, U.S. Pat. No. 4,919,461 to Reynolds discloses a pressure cylinder having a body, an insert fitting threadably engaged within the cylinder, and a pipe retained within the body by an intermediate pipe nut having a threaded connection with the insert fitting. An O-ring is retained in a groove in the insert fitting, piloting in a reduced diameter of the body.
Lastly, U.S. Pat. No. 5,310,227 to Grinsteiner discloses a conduit assembly including an intermediate compression fitting adjacent a seal, that in turn is adjacent a retainer ring. The sleeve, seal, and retainer ring are attached to a body conduit by an intermediate fitting threadably engaged to a fitting body.
Unfortunately, each of the above-mentioned references discloses a component made of a multitude of intermediate parts. The connectors in each of the above-mentioned references is held in place on a conduit by some type of threaded engagement, either directly with the insert, or among intermediate components surrounding the insert that are threadably engaged to each other.
Consequently, the prior art couplings described above are not optimal for use in a vehicular air-conditioning system because they have limited capability to withstand the harsh environment of the engine compartment. Conduit in a vehicular air-conditioning system is subject to extreme variations in temperature. In cold weather the couplings are subjected to temperatures ranging from as low as -40.degree. F. (-55.degree. C.) to around 260.degree. F. (127.degree. C.). In warm weather, temperatures under the hood can exceed 260.degree. F. (127.degree. C.). The multiple interconnections between the component couplings described above are not durable enough to withstand such temperature variations over extended periods of time. Each of the different components of the multiple component couplings have different expansion properties. Therefore, the retainer cap, retaining ring, and threaded nut required in the multiple component couplings are not reliable enough in a setting exposed to extreme temperature variations.
Furthermore, the couplings described above are also not suitable for the high pressure, harsh vibration conditions that exist under the hood of a car. The couplings described above connect two conduits to each other. They are not proper, however, for connecting conduits that are subject to high pressure, harsh vibrations, and extreme temperature variations where the multiple components are likely to be shaken apart or loosened due to the vibrations of the engine. The threaded connections relied on by the prior art couplings are simply more liable to fail in such a harsh environment due to leakage.
Accordingly, different types of solutions to the temperature and vibration problems associated with such devices have been proposed. For example, U.S. Pat. No. 3,778,090 to Tobin (hereinafter '090) discloses a thin walled beaded conduit connection for securing a conduit to a manifold block with an O-ring seal thereon. The conduit, extending through a counterbored aperture in the conduit block, is upset at one end to form an annular bead for axially locating the conduit to the block. Concurrently, the conduit is expanded to flow material into grooves circumscribed within the block aperture, for axially locking the conduit to the block. At a second surface, an O-ring encircles the conduit and pilots into a counterbore in the block. This second surface is then upset to form a second annular bead for axially compressing the O-ring and axially locking the block between the two annular upset beads.
Similar to the above patent is U.S. Pat. No. 5,092,634 to Miller (hereinafter '634). This reference is substantially similar to the '090 reference and is a connection for securing a conduit to a manifold block. This reference, however, incorporates a washer sandwiched between the second upset bead and the O-ring to improve O-ring compression and surface contact. Unfortunately, both of the above references are still susceptible to the problems of contamination. During the bead upsetting process the upset bead scrapes the counterbore of the body thereby generating contaminants. These contaminants cut into and degrade the O-rings that reside in the same counterbore, thereby leading to leaks and premature failure of the connection.
Alternatively, a further solution is proposed in U.S. Pat. No. 3,787,945 to Pasek et al. (hereinafter '945). This reference proposes providing a stepped bore in a conduit block, and inserting a thin walled conduit into a first surface of the stepped bore with an O-ring encircling the conduit. Moreover, this reference further proposes expanding the conduit within the stepped bore to compress the O-ring and axially locate the conduit against the step in the bore. Simultaneously, a second surface of the conduit is upset to form an annular bead to lock the block between the annular bead and expanded end of the conduit.
Therefore, the '945, '634, and '090 references all require use of several steps and design features to axially lock and seal the conduit to the block. Additionally, this prior art entraps the block to the conduit between two opposed enlarged diameters, or beads, in the conduit. Although this results in an initial positive axial entrapment, there are several problems. First, the upset beads are the weak link in the conduit because they undergo significant material deformation and over-compression in the fold of the bead. This deformation leads to conduit thinning and cracking in the bead. In turn, the thinning and cracking of the bead can lead to leaks resulting in premature conduit failure under harsh environmental conditions. Second, in addition to a thinned and cracked bead area, the conduit material is relatively soft and subject to harsh environmental forces. Therefore the bead strength that is relied upon for axial locking eventually gives way as the material "creeps," and results in an axially slack connection. This slack permits slight relative motion between the O-ring and the sealing surfaces, thereby leading to premature O-ring wear, failure, and leakage.
Finally, aside from all the prior art mentioned above, there are other conventional conduit end-forming methods generally known in the art. These methods involve time consuming, inaccurate manufacturing processes that result in parts with relatively large variances in dimensional tolerances. A closer tolerance between conduit and body can eliminate assembly O-ring seal defects such as side loading. One current method involves forming an upset bead on a conduit then inserting a connector block over a conduit end so that it abuts the bead and the conduit end extends a predetermined distance beyond the connector block. The conduit end undergoes a process that compresses the length of conduit that extends beyond the block from front to back. This compression encapsulates the inside and outside diameters of the conduit, and in turn, increases the wall thickness of the conduit, thereby creating a pilot. Then, the pilot is shaved during a secondary process that grips the conduit behind the connector block, thereby causing dimensional variances. Lastly, a shaver-cutting tool surrounds and machines the pilot and O-ring grooves.
Consequently, one problem experienced with this method is that the grip on the conduit is at such a distance from the pilot end that the conduit flexes, bends, and twists under pressure from the cutting tool. This flexing movement causes dimensional variations that can lead to a non-concentric end-form. As a result, the O-ring groove tends to be cut too deep, and when the conduit connection is made, the O-ring is pinched at one side causing decompression on the opposite side. The area of the O-ring that is not fully compressed is a leak path for refrigerant fluid. Throughout the life of the seal, small leaks can occur sporadically in the harsh automotive engine compartment that are difficult to trace, and lead to loss of refrigerant fluid.
Another problem is that the length of the cutting tool enables the tool to vibrate as it cuts, thereby leading to a defective end-form. The surface of the end-form gets marred and the O-ring groove may be irregularly shaped. These "chattering" defects, enable leaks under the extreme temperatures and pressures in an air-conditioning system.
What is needed is a fluid-tight conduit connection that has a minimum of design features and processing steps; is easily manufactured; has stable dimensional tolerances; and eliminates end-form defects associated with current end-forming technology, such as side load defects, chattering, and contamination. Further, what is needed is a fluid-tight conduit connection and associated method, where the connection is virtually integral between the parts being connected, and where the conduit is expanded to sealingly interlock the conduit to at least one recess in the body. Such a device will overcome the problems associated with multiple component connectors, contaminants generated during the end-forming process, and other defects associated with conventional conduit connection end-forming processes.